Corneal endothelial cells (CECs) play a highly important role in maintaining transparency of the cornea. However, CECs are said to proliferate and regenerate little in an organism (the human body). When CECs are injured, the injured area does not fill with proliferating cells; instead, the injury heals by a mechanism where the surface area of the cells is increased to fill the gap through the extensional migration and compensatory expansion of cells. As a result, the density of CECs per unit of surface area decreases. Accordingly, for example, when the injury heals through expanding the surface area of CECs, functioning of the cornea is self-limiting; when torn, disorders such as bullous keratopathy result. In that case, the conventional treatment has been a cornea transplant. However, in Japan at least, there is an acute shortage of cornea donors. There is also the problem of tissue compatibility when conducting a transplant. Treatment by corneal transplant is thus far from being an ideal solution.
As shown in FIG. 8, the cornea 1 is comprised of a multilayered structure: the anterior corneal epithelium 2, Bowman's membrane 3, the corneal stroma 4, Descemet's membrane 5, and the corneal endothelial cells 6. When preserved over time, the corneal epithelial cells are left out, the corneal stroma swell, and the endothelial cells decrease. Concerning to the corneal epithelial cells and the stromal cells, these are not problem because of their ability to regenerate. However, as stated above, the CECs have a poor ability to proliferate, so that when the cornea is stored for an extended period, there is a problem in that the endothelial cells decrease. That is, in the case of a cornea is transplanted, the method of storage may lead to a problem in decrease of endothelial cells.
Thus, there is a problem in that the CECs have an extremely poor ability to proliferate within the organism. Accordingly, in an attempt to regenerate CECs having an extremely poor ability to proliferate within the organism, a method of reconstructing the cornea has been proposed in which cultured CECs are planted on the corneal stroma from which endothelial cells have been removed, and a layer of CECs is built on the stroma (Japanese Unexamined Patent Publication (KOKAI) No. 2002-78723).
However, since the above-described method presents problems in that it requires a cornea from which the endothelial cells have been removed, the method does not provide a solution for a shortage of cornea donors, and for an inability to handle the rejection accompanying a transplant. Further, it is possible to remove the cornea of the patient for a certain period so that a corneal endothelial cell layer can be rebuilt on the cornea. However, while the corneal endothelial cell layer is being reconstructed, the patient must do without sight and is greatly burdened in his daily life.
Accordingly, the object of the present invention is to solve these problems by providing a laminate of implantable cultured endothelial cells layer.